1. Field of the Invention
This invention relates to the art of reclosable bags of the type generally fabricated from plastic film, and is more particularly concerned with a new and improved reclosably separable resiliently flexible extruded plastic fastener profile assembly for such bags.
Bags of the type indicated are in widespread use for enveloping contents retained in the bags by means of the separable and reclosable fasteners at the top, or mouth ends, of the bags and providing convenient means for access into the bags when desired.
Separable fasteners have attained a considerable degree of development. One common construction consists of a single rib and groove assembly having a generally asymmetric arrowhead shaped cross-section male fastener member on one wall of the bag and a complementary grooved female profile on the opposite wall having hook shaped structure interlockable with the arrowhead shaped profile. A problem with such a single rib and groove fastener profile structure is that unless the structure has a certain size or stiffness and is manufactured to fairly exacting dimensions some difficulty is often encountered in effecting registration of the complementary profiles in fastener closing maneuver thereby making the fastener more difficult to interlock. On the other hand, this type of fastener structure has the advantage that the profile elements can be easily and economically provided with a construction that retains the fastener securely against opening due to internal pressures within the bag, such as may be caused by air or the contents in the bag that exert separating force on the bag walls, and nevertheless, can be readily opened from the outside by pulling the same apart as by means of pull flanges which extend outwardly at the mouth of the bag.
In another form of separable fastener there is provided a plurality of parallel interlockable hook shaped ribs, which even in a relatively very small size and relatively soft and resiliently flexible material can be readily aligned for closing by simple inward pressure. However, this type of separable fastener does not lend itself readily to resistance against internal pressure, and has heretofore required a supplementary expedient such as hingedly connecting one of the fastener profiles to overcome the problem.
2. Prior Art
The following U.S. patents are referred to as exemplary of the present state of the art:
U.S. Pat. No. Re. 28,969--shows a single arrowhead profile and complementary groove profile and with a structure at the side of the fastener facing toward the inside of the bag to resist separation due to internal outward pressures on the sidewalls.
U.S. Pat. No. 3,416,585--another example of a single rib and groove arrangement with structure to resist opening of the fastener from internal pressures.
U.S. Pat. No. 3,389,733--a further example of single rib and groove arrangement with means to resist opening of the fastener from internal pressures.
U.S. Pat. No. 3,425,469--still another example of a single rib and groove fastener structure having means to resist opening from the inside of the bag.
U.S. Pat. No. 3,372,442--shows an arrangement wherein a single arrow shaped profile is partially split and receives a wedge shaped prong rib projecting from the root of the grooved profile, and the structure being such as to resist opening due to internal pressures in the bag.
U.S. Pat. No. 3,633,642--aims to attain equal opening of the fastener from either inside or outside and provides fairly massive pull flange areas on which the fastener profiles are carried.
U.S. Pat. Nos. 2,780,261 and 3,054,434--show arrangements of fastener profile sections each comprising a plurality of ribs and grooves, and wherein one of the profile sections is carried on a hinge attached to the adjacent bag wall to afford expansion capability of the bag without separating the fastener due to internal pressures. These patents are representatives of numerous patents showing similar hinged mounting of one of the fastener profile sections.